examples/android/media_demo/build.xml

<?xml version="1.0" encoding="UTF-8"?>
<project name="WebRTCDemo" default="help">
    <property file="local.properties" />
    <property environment="env" />
    <condition property="sdk.dir" value="${env.ANDROID_SDK_ROOT}">
        <isset property="env.ANDROID_SDK_ROOT" />
    </condition>
    <loadproperties srcFile="project.properties" />
    <fail
            message="sdk.dir is missing. Make sure to generate local.properties using 'android update project' or to inject it through the ANDROID_SDK_ROOT environment variable."
            unless="sdk.dir"
    />
    <import file="custom_rules.xml" optional="true" />
    <import file="${sdk.dir}/tools/ant/build.xml" />
</project>